Breakaway Guardrail Post for a Highway Crash Attenuation System

ABSTRACT

A highway crash attenuation system having an improved breakaway guardrail post. An improved upper section of Post 1 has an anchor bearing plate with a cooperating stabilizing bolt engaging with the upstream face of the upper post section. The downstream side of the upper post section is provided with split, spaced-apart strut sections which do not obstruct the rear cable pass through notch.

BACKGROUND

The present invention relates to improvements to energy absorbingguardrail systems having end terminals, anchor cable release mechanisms,and breakaway posts used in cooperation with longitudinal, sectionalbarriers. These systems usually extend along highways and roadsides toabsorb impact energy and deflect vehicles from hazards which may beassociated behind the barriers. The present invention more specificallyrelates to systems having Box-Beam terminals, sequential kinkingterminals (SKT) and flared energy absorbing terminals (FLEAT). Moreparticularly, the present invention relates to an improved breakawaypost (Post 1) which facilitates breakaway in head-on impacts whileresisting loads on side impacts. Each of these improvements may beincorporated into existing energy absorbing guardrail systems, alone orin combination, to improve the overall safety performance of thesystems.

Existing Box-Beam, SKT, and FLEAT terminals depend on the breakaway ofPost 1 to release the upstream end of an anchor cable. However, undercertain impact conditions, Post 1 may not break away properly, thus notreleasing the anchor cable. This in turn could result in snagging andexcessively high deceleration of the impacting vehicle. In some casesduring an end-on hit, after Post 1 released and lifted the anchor orbearing plate, the assembly got caught under the vehicle resulting intears in the vehicle's floorboard.

The fact that the cable did not fully separate from the upper section ofPost 1 appeared to be the cause of snagging and tearing problems. Apresent improvement to the first upper section of Post 1 provides amechanism to positively lift the bearing plate off of the lower sectionof Post 1 and allow Post 1 to separate from the anchor cable.

In earlier Post 1 designs, Post 1 was intended to breakaway when thepost was impacted from a head-on direction, but the post had limitedlateral strength. Thus, for side impacts just downstream of Post 1, theearlier Post 1 design sometimes resulted in unintentional break awayallowing the impacting vehicle to gate through the terminal and gobehind the guardrail installation. An embodiment of the presentinvention provides for an improved post design that still allows Post 1to break away in head-on impact, while providing added lateral strengthto accommodate side impacts just downstream of Post 1.

An alternative embodiment of the present invention utilizes the anchorcable release bracket disclosed and claimed in U.S. Pat. No. 8,448,913,but utilizes an improved upstream anchor cable release mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a side elevation view of an SKT highway guardrailterminal system having the improved breakaway guardrail post of thepresent invention.

FIG. 1A shows a top plan view of the terminal of FIG. 1.

FIG. 2 illustrates a side elevation view of a Box-Beam highway guardrailterminal having the improved breakaway guardrail post of the presentinvention.

FIG. 2A shows a top plan view of the terminal of FIG. 2.

FIG. 2B illustrates a detailed view of the improved breakaway post ofthe present invention in a first aligned position prior to impact.

FIG. 2C illustrates a side elevation view of the lower post sectionshowing a ledge or shelf on the upstream face of the post section.

FIG. 2C ¹ shows a top side view of the lower post section.

FIG. 2C ² illustrates a bottom side view of the lower post section.

FIG. 2C ³ shows a side elevation view of the lower post section.

FIG. 3 shows a downstream perspective view of the improved breakawaypost of the present invention in a first aligned position.

FIG. 3A illustrates a front elevation view of the upper section of theimproved breakaway post showing a front, lower anchor cable pass throughnotch, an angle iron spacer, and anchor stabilizing bolt hole.

FIG. 3B illustrates a side elevation view of the upper section of theimproved breakaway post showing an angle iron spacer on the upstreamside of the post section and a section of lateral support lip or strutalong a lower edge of the downstream face of the upper post section.

FIG. 3C shows a rear elevation view of the upper section of the improvedbreakaway position of FIG. 3A showing a rear notch and the spaced apartsection of lateral support lips extending along the lower edge of thedownstream face of the upper section. The spaced-apart lip sections havea space therebetween such that the rear notch opening is unobstructed.

FIG. 3D is a top view of the upper post section of FIG. 3C showing thespaced-apart sections of the lateral support lip with a spacetherebetween for an anchor cable to pass through.

FIG. 3E illustrates the anchor bearing plate used in association withthe upper post section showing the stabilizing bolt hole and the anchorcable through pass hole.

FIG. 3F illustrates a side elevation view of the improved breakawayguardrail post with the upper section in rotation and lifting of thelower post section upon a head-on impact.

FIG. 4A is a detailed view of the components of the improved breakawaypost of FIG. 4A.

FIG. 4B shows the anchor bearing plate of the improved breakaway postpreventing lateral rotation of upper section in relation to lowersection.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Referring now to the drawings, and more particularly to FIG. 1, thereference numerical 12 a generally represents an SKT energy dissipatingguardrail terminal with the improved breakaway guardrail post of thepresent invention. The terminal is adapted to be connected to theupstream side of a conventional guardrail 14 a consisting of standardW-beam guardrail sections. The guardrail sections or rail elements areattached along their vertical axes V by bolts 22 to a plurality ofspaced apart vertical breakaway posts 116 a-116 b. Any suitable numberof posts may be used depending upon the expanse of the guardrail run.FIG. 1 illustrates two steel breakaway posts. Steel posts downstreamfrom lead posts 116 a and 116 b may be embedded directly into the soil.

FIG. 1 further illustrates the anchor cable mechanism 24 which includesan anchor cable 26, a lower anchor cable bolt 28, and an anchor cablerelease bracket 30 a. The anchor cable mechanism is provided to allowthe terminal to withstand angular vehicle impacts downstream of itsupstream end.

FIGS. 2 and 2A show a Box-Beam bursting energy absorbing terminal withthe improved breakaway guardrail post of the present invention.

It is intended that a vehicle will impact the guardrail downstream ofits upstream end; however, a collision with the upstream end requiresthe provision of an end treatment to reduce the extent of injury to theimpacting vehicle and its occupants. The purpose of the end treatment isto dissipate impact energy of the vehicle. There are a number ofexisting prior art treatments which are compatible with the instantinvention, including, but not limited to, the Box-Beam terminal,sequential kinking terminal (SKT), and other bursting energy terminal(BEAT).

As seen in FIGS. 1 and 1A, the impact head portion 50 a of the endtreatment is attached on the upstream end of a guide tube or feederchute 48 a. Guide tube 48 a is mounted onto improved breakaway lead post116 a by fasteners passing through post angle brackets. The upstream endof the W-beam rail element 14 a extends into the guide tube 48 a. Guidetube 48 a has an anchor bracket impact shoulder 102 with a leadingtapered edge which impacts with the upstream end of anchor cable releasebracket 30 a when the impact head 50 a is urged downstream upon avehicular impact.

When the end treatment is impacted end-on by an errant vehicle, animpact plate 72 will engage and interlock mechanically with the front ofthe vehicle. As the vehicle proceeds forward, the impact head 50 a willbe moved forward or downstream along the W-beam rail element 14 a.Improved breakaway Post 116 a is provided with a hole through whichpasses the upstream end of the anchor cable 26. When the impact head isdisplaced downstream in a collision, post 116 a will snap or break asdiscussed below, thus releasing the tension on the cable 26 of theanchor cable mechanism 24 at this upstream location.

At or shortly after breaking the lead post 116 a, the upstream end ofthe W-beam rail element 14 a will be treated within the impact head todissipate impact energy. As the vehicle proceeds forward and pushes theimpact head 50 a along, the downstream end of the guide tube/feederchute 48 a reaches the upstream end of anchor cable release bracket 30 aon the rail element 14 a. The anchor cable release bracket, which isheld on the W-beam rail element 14 a by the anchor cable release bracketattachment bolts, will be pushed forward, slide off the bolts, rotateout of parallel alignment with and be released from the W-beam railelement 14 a. This process is fully described in U.S. Pat. No.8,448,913, which is incorporated herein for all purposes.

FIG. 1A is a top view of the FIG. 1 highway guardrail system with theimproved breakaway guardrail post 116 a. Details of the structure andoperation of the prior art cable release mechanism are taught anddisclosed in U.S. Pat. No. 8,448,913 B1 issued May 28, 2013, whichdisclosure is incorporated herein for all purposes.

Turning now to FIGS. 2 and 2A, a Box-Beam terminal system 12 b is shownwith an improved breakaway guardrail post 116 a. U.S. Pat. No.6,308,809, which is incorporated herein for all purposes, teaches acrash attenuation system which uses a controlled fracture mechanism.FIG. 2 illustrates a side elevation view of such a crash attenuationsystem mounted on guardrail posts 116 a and 116 b. The attenuationsystem has an anchor cable release mechanism 24 which cooperates withimproved breakaway guardrail post 116 a to control the rotation of theupper post section 200 off of the lower post section 202 as discussedbelow.

The Box-Beam terminal 12 b has a controlled fracture or rupturingmechanism wherein an oversized plunger with a tapered surface (mandrel13) is forced into a thin-wall tubing 14 of the generally same shapewhereby pressure is exerted on the edges of the tubing from inside. Thepressure initially expands the size of the thin-wall tubing, firstelastically until the yielding strength of the material of the tube isreached and then plastically. The tubing eventually fractures orruptures at the edge when the ultimate tensile capacity of the materialis exceeded. This process of fracturing the tubing dissipates energy asthe mandrel proceeds downstream.

FIG. 2B illustrates the components of the improved breakaway post 116 aused with highway crash systems relying upon a lead breakaway posthaving an upper post section 200 and a lower post section 202. FIG. 2Bshows the post 116 a in a first aligned position.

As may be seen in FIG. 2B, lead post 116 a has an upper post section 200provided with a section of angle iron 410 on the upstream face 200 a ofpost section 200. The angle iron 410 acts as a spacer between anchorbearing plate 406 and the upper post section 200. The spacer 410enhances engagement of the bearing plate 406 with the lower post section202. The size of the angle iron 410 urges the bearing plate to assume apredetermined angle (angle range of 0° to 70°) from the vertical. Thisangle significantly reduces the propensity of the bearing plate 406 toslip up and off the lower post section 202 during a redirective impactwhere the load is applied via the cable 26 to the bearing plate 406.

FIG. 2B also shows an L-shaped ledge or shelf 412 extending from theupstream face 201 of lower post section 202 upon which a lower edge ofthe bearing plate 406 rests atop of the ledge 412 to mitigate therotation of the bearing plate 406, which may reduce the anchoragecapacity of the system.

FIG. 2C illustrates that the top 207 of the lower post section 202extends upstream of the face 201 of the lower post section to providethe ledge or shelf 412. FIGS. 2C ¹-2C³ illustrate top side, bottom side,and side elevation views of lower post section 202 showing therelationship of the ledge 412. A vertical crossmember 413 extendshorizontally along an upstream portion of the top to complete theL-shaped shelf 412.

Additionally, FIGS. 2C-2C ³ illustrate that the height h (FIG. 2C ³) ofopposing, upwardly-extending side plates 414 and 416 on the top 207 ofthe lower post section 202 are raised to a location above the centerlineof an anchor cable locking nut 28 a affixed to the upstream-most end ofthe anchor cable 26 when the cable 26 passes through through hole 29 bin plate 406, through through notch 225 and notch 227 in upper postsection 200 (see FIGS. 3A-3F).

FIG. 3 shows a downstream perspective view of the improved post in afirst aligned position. As stated previously, this improved post may beused with any terminal which requires a lead breakaway post.

FIG. 3A illustrates a front elevation view of the improved upper section200 of Post 1 116 a, showing a front, lower anchor cable pass throughnotch 225, an angle iron space 410 affixed to the upstream face ofsection 200, and an anchor stabilizing bolt hole 500.

To provide the positive release of the bearing plate 406 a (FIG. 3F), anadditional anchor bolt stabilizing hole 502 is provided through thebearing plate 406. An anchor plate stabilizing bolt 504 (FIG. 3F) may besecured in a manner that protrudes into the stabilizing hole 500 on theupstream face of Post 1 (FIG. 3F).

In an end-on impact, the engagement of bolt 504 with the hole 500 inPost 1 lifts the bearing plate 406 a off of lower section 202 of Post 1as illustrated in FIG. 3F. This improvement involving the cooperation ofthe bolt 504 with the hole 500 in Post 1 allows upper section 200 ofPost 1 and the bearing plate 406 a to be free to detach, reducing thebulk of the assembly 400. Crash testing with this modified arrangementwas successful with no damage to the floor pan of the impacting vehicle.

FIG. 3B shows a side elevation view of a modified upper post section 200with angle iron space 410 on the upstream face of the section 200. Onthe downstream face at the bottom of the section 200 is sectioned rearstrut or strap 214 a. FIG. 3D shows, from a top view, the sectioned rearstrut (204 a and 204 b) along the base of the section 200. It was foundthat the strut did not need to extend along the entire downstream face,but that the spaced-apart section portions 204 a and 204 b still engagethe lower post section 202 and function effectively.

The spaced-apart, section portions 204 a and 204 b may be seen in FIG.3C along the lower bottom edge of the section 200. Further, FIG. 3Cshows the cable pass through slots or notches 225 (in the upstream faceof section 200) and 227 (in the downstream face of section 200).

An anchor bearing plate 406 is illustrated in FIG. 3F. The additionalstabilizer bolt hole 502 is shown above the cable hole 29 b.

FIG. 3F is similar to FIG. 2B, except that it illustrates the anchorassembly with the stabilizing bolt 504 passing through the bearing plate406 a and into the upstream face of upper section 200 of Post 1 as upperpost section 200 rotates and lifts off lower section 202 upon impact.

FIG. 4A, 4A ¹, and 4B illustrate how anchor bearing plate 406 cooperateswith ledge 412 to avoid lateral rotation of the plate 406. Thestabilizing bolt 504 further enhances the avoidance of rotation of theplate 406. The reference numerals in FIGS. 4A, 4A ¹, and 4B areconsistent with those used in the above discussion.

The embodiments described herein are some examples of the currentinvention. Various modifications and changes of the current inventionwill be apparent to persons of ordinary skill in the art. Among otherthings, any feature described for one embodiment may be used in anyother embodiment. The scope of the invention is defined by the attachedclaims and other claims to be drawn to this invention, considering thedoctrine of equivalents, and is not limited to the specific examplesdescribed herein.

What is claimed is:
 1. A highway crash attenuation system having animproved breakaway guardrail post said post comprising: an upper postsection and a lower post section, said upper post section having a firstanchor cable through notch in an upstream wall of said upper postsection and a second notch in a downstream wall of said upper postsection, said anchor cable passing through said first notch in saidupstream wall and said second notch in said downstream wall;spaced-apart sections of lateral support lips extending along a loweredge of a downstream face of said upper post section, said spaced-apartsupport lip sections having a space therebetween such that a cable passthrough opening in said second notch is unobstructed; a cable anchorbearing plate engaged with an upstream face of said upper post section,said bearing plate having a first anchor cable through hole throughwhich an anchor cable is adapted to pass and be retained therein by alocking nut affixed to an upstream most end of said anchor cable,wherein said bearing plate is disposed at a predetermined angle withrespect to said first breakaway post by engaging a spacer between a topend of said plate and an upstream face of said upper post; and an anchorbearing stabilizing bolt extending through a second hole in said bearingplate and secured in a stabilizing hole in said upstream face of saidupper post section.
 2. The highway crash attenuation system of claim 1,wherein said spacer is a section of angle iron joined with said upstreamface of said upper section of said post.
 3. The highway crashattenuation system of claim 1, further comprising: a ledge on top ofsaid lower section of said post, said ledge extending under said cableanchor bearing plate to provide a shelf for supporting said bearingplate and preventing rotation of said cable anchor bearing plate.
 4. Thehighway crash attenuation system of claim 3, wherein said upstream-mostend of said anchor cable remains retained by said cable anchor bearingplate after vehicular impact separating said upper post section fromsaid lower post section.